Demographics and functional response of Blaptostethus pallescens preying on Tuta absoluta

Phytoparasitica - In order to enhance the ecofriendly management of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), we studied the demographics and functional response of Blaptostethus...     

Breeding Potential of Potato Somatic Hybrids: Evaluations for Adaptability,Tuber Traits,Late Blight Resistance,Keeping Quality and Backcross (BC<Subscript>1</Subscript>) Progenies

Ten tetraploid interspecific potato somatic hybrids developed earlier through protoplast fusion between the dihaploid Solanum tuberosum L. ‘C-13’ and the diploid wild species Solanum pinnatisectum Dun. were used in this study. Somatic hybrids and standard control cultivars were evaluated for adaptability, tuber traits, late blight resistance and keeping quality attributes (dormancy, sprouting, weight loss and appearance after 75 days of storage) during two successive winter crop seasons (short-days) in the sub-tropical plains of India, where nearly 90% of India’s potatoes are grown. Somatic hybrids showed medium to good plant vigour and late to very late plant maturity. Though none of the somatic hybrids produced equal or higher tuber yield than the control cultivars, except clone P7, all other somatic hybrids produced significantly higher marketable and total tuber yield after a 90-day growth than the parent C-13. Most of the somatic hybrids possessed higher tuber dry matter concentration, resistance to late blight and better keeping quality attributes than the control cultivars. Notably, the tubers of somatic hybrids showed a tendency for colour change from white to purple on exposure to sunlight. Breeding potential of somatic hybrids was further assessed by crossing them with commonly grown local potato cultivars for the development of backcross (BC₁) progenies. In the hybridization programme, berries were formed while somatic hybrids were used either as male or female parents with common cultivars. Our results revealed that the use of bulk pollen of somatic hybrids not only resulted in higher pollination success but also helped to achieve higher numbers of true potato seeds (TPS) per berry. Despite the formation of berries, TPS was absent in 22 crosses using somatic hybrids as a female or male parent which may be due to ovule or embryo abortions. Segregating BC₁ generations were evaluated under the same sub-tropical conditions for further exploitation in potato breeding. Based on our study, the somatic hybrids P4, P8 and P10 can be utilized for the introgression of important characters such as high tuber dry matter concontration, resistance to late blight and excellent keeping quality attributes into the cultivated potato via conventional breeding methods for cultivar development in the sub-tropical plains of India.     

Integrated Management of Whitefly, Bemisia tabaci (Gennadius) and Potato Apical Leaf Curl Virus in India

This paper reviews the importance of Potato apical leaf curl virus (PALCV) in India, the biology of its major vector Bemisia tabaci and possible control measures of PALCV and B. tabaci. PALCV has appeared as a new problem in potato growing areas of northwestern plains of India. The first report of PALCV was made from Hissar around 2000. PALCV is a whitefly (B. tabaci) transmitted viral disease and the symptoms are manifested primarily in the form of upward or downward curling of leaves, with 40–75% infection being recorded in cultivars grown in the Indo-Gangetic Plains of India. B. tabaci is a polyphagous pest that feeds on numerous fibre (particularly cotton), food, vegetable and ornamental plants. B. tabaci produces many generations in a year and reaches high population densities. To check the disease incidence, whitefly suppression using imidacloprid either as seed treatment or as foliar application early in the season is recommended. To minimize within-field spread of viruses, removal of virus-infected plants is suggested. Application of mineral and vegetable oils has been found to inhibit virus transmission and possibly can help to avoid difficulties with insecticide resistance in whiteflies.     

Functional response of <Emphasis Type="Italic">Harmonia dimidiata</Emphasis> (fab.) to melon aphid, <Emphasis Type="Italic">Aphis gossypii</Emphasis> Glover under laboratory conditions

Functional response of Harmonia dimidiata (Fab.) to melon aphid, Aphis gossypii Glover was studied in the laboratory at 25 ± 0.5 °C, 70 ± 5% RH and 12L:12D photoperiod. All the predator stages exhibited Type II functional response to the aphid. Based on Rogers’s random predator equation the predator’s attack rate was lowest (0.128) in the first-instar and highest (0.21) in the adult stage. Handling times of the adult beetle and the fourth-instar (0.148 and 0.164 h, respectively) were much shorter than other stages. The maximum number of aphids that could be consumed over a period of 24 h by first, second, third and fourth instar; and adult of H. dimidiata was estimated to be 47.2, 80.2, 79.7, 146.2 and 161.7 aphids/ predator. Functional response parameters indicate that the adult beetles and the fourth-instar were the most voracious stages and could be important for the biological control of the aphid.     

Comparative efficacy of indigenous heterorhabditid nematodes from north western Himalaya and Heterorhabditis indica (Poinar,Karunakar & David) against the larvae of Helicoverpa armigera (Hubner)

The efficacy of three Heterorhabditis spp of entomopathogenic nematodes (EPNs) from north western Himalaya, India was studied against the larvae of pod borer, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), under the laboratory conditions. The larvae were exposed to 10, 20, 30 and 40 infective juveniles (IJs) of each nematode species for different time periods and they were found to be susceptible to all the EPNs tested. However, the susceptibility of larvae to nematode infection varied according to the concentrations of IJs and their exposure periods. The efficacy of these indigenous entomopathogenic nematodes was also compared against commercially available entomopathogenic nematode, H. indica. Appreciably good performance was achieved by H. bacteriophora (HRJ), which showed 73.3% mortality of insect larvae in 96 h exposure time against third instar larvae, while H. indica produced 80.0% mortality. However it was noticed that with the advancement of larval stage its mortality rate reduced and vice versa with the exposure period. All tested EPNs were also found to reproduce within the host and maximum production of IJs was recorded in H. bacteriophora (26.0 ± 3.76 × 10³ IJs/larva) at the concentration of 40 IJs/larva.     

Occurrence of Prunus necrotic ringspot virus on nectarine (Prunus persica) in India

This paper presents the results of the first survey for Prunus necrotic ringspot virus (PNRSV) on nectarine ( Prunus persica ) in India, where stone fruits are grown on a commercial scale. Using basic diagnostic techniques such as ELISA and RT-PCR, the occurrence of Prunus necrotic ringspot virus is reported for the first time on nectarine ( Prunus persica ) in India.     

Soil Quality Assessment Through Minimum Data Set Under Different Land Uses of Submontane Punjab

Soil quality degradation is a major challenge in submontane Punjab. This poses a great threat to soil quality of this particular area. Thus, a study was conducted to address the selection of most appropriate soil quality indicators and to know the status of soil quality in the area under different land uses. Principal component analysis (PCA) approach was employed to get the minimum data set. Geo-referred soil samples were collected from five different land uses and analyzed for different physical, chemical, and biological attributes. The PCA was performed which screened out the five principal components (PCs) with eigenvalue >1. Soil quality index was highest under the land use forest (0.80) followed by grasses (0.79), horticulture (0.78), cultivated (0.75), and bare (0.67). The organic carbon contributed maximum to soil quality (28.5%) followed by available K (19.4%), electrical conductivity (18.3%), K-factor of universal soil loss equation (USLE) (14.9%), plant available water (10.5%), and clay (8.3%). Conclusively, the study area falls under the medium category of soil quality.